System and method of providing quality of service-enabled contents in peer-to-peer networks

ABSTRACT

A system and method of providing quality of service (QoS)-enabled digital content in peer-to-peer (P2P) networks are provided. The QoS-enabled service system on the P2P network includes: a service provider capable of providing digital content; one or more user nodes receiving digital content from the service provider; one or more donor nodes lending resources for providing digital content; and a supernode receiving information on user nodes and donor nodes, and a copy of digital content from the service provider, allowing the exchange of digital content among the user nodes through P2P networking, and when at least one user node experiences a P2P networking error during the exchange of the digital content, arranging for a predetermined number of donor nodes from among the one or more donor nodes to join the P2P networking. According to the system and method, even when the function of a peer does not normally work on a P2P network, a donor as a replacement of the peer is utilized, thereby providing QoS-enabled digital content to a user requesting the digital content.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2007-0020584, filed on Feb. 28, 2007, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Systems and methods consistent with the present invention relate to apeer-to-peer (P2P) network, and more particularly, to of supportingquality of service (QoS)-enabled digital content in a P2P network.

2. Description of the Related Art

Peer-to-peer (P2P) is a technology which enables a computer of a personwho is seeking information and a computer of a person who has theinformation to be connected directly without a server computerin-between on the Internet, thereby allowing the information to beshared, and a new service to be provided by applying the P2P technology.Unlike the conventional method requiring a search engine for findinginformation on the Internet, information can be received directly fromany personal computer (PC) connected to the Internet, and in addition tosearching downloading can even be performed.

P2P technology applies the concept of a local area network (LAN) to theInternet. If P2P technology is used, PC users can freely access eachother's computers without a separate server or a fixed IP address(dedicated line), and exchange required data. Accordingly, ordinary PCusers can directly exchange MP3 files or other computer files with eachother without an intermediary, and in relation to Internet businesses,this P2P technology can be applied to a wide variety of fields.

A P2P network has an ad-hoc structure in which dispersed nodescommunicate with each other without any central control, and eachparticipating node can perform both a router role and a server role. TheP2P network is applied to an environment that does not requirecontinuous connection.

All nodes participating in a P2P network permit other nodes to accessrespective resources, thereby participating in the P2P network. Withouta separate central management system, each node provides a cooperativeservice among participants.

File sharing is a representative type of P2P application service. Aclient node which downloads a file in a P2P environment also providesthe file to other nodes, thereby also performing a server role.Providing presence information of nodes and resources in a P2P-basedvoluntary structural organization is a basic function of the P2P system.Thus, a node can directly communicate with other nodes and can send aquery about a required resource.

As file sharing programs of a P2P system, Napster and Gnutella have beendeveloped, followed by KaZaA which is now widely used. A characteristicof KaZaA is that after finding a plurality of users having identicalfiles, the file is divided into smaller parts, and the smaller parts aredownloaded at the same time from a plurality of places. For example, ifthe file is downloaded from three places, the download can be finishedthree times faster than downloading from one place.

Another characteristic of KaZaA is that searching is performed by usinga supernode method. This can be regarded as a compromise between theNapster method in which searching is centrally performed, and theGnutella method in which searching is performed in a completelydistributed manner. Among users' computers, those computers withrelatively larger capacities are selected and referred to as supernodes.In each supernode, the list of files shared by the users neighboring thesupernode is stored. When a user begins searching, the user sends asearch request to a supernode to which the user is connected, and then,the request is also transferred to other supernodes.

However, in this P2P network, the connection of each peer is dynamic,that is, according to user's circumstances, the related node may beirregularly disconnected from or connected to the network. Accordingly,if one node having a predetermined file is disconnected, a download planof another node to obtain data from the disconnected node may fail. As aresult, this transient characteristic of the P2P network cannotguarantee the data transmission performance, thereby making theoperation of the network unpredictable. Accordingly, a service forproviding QoS-enabled digital content may not be performed normally.

SUMMARY OF THE INVENTION

The present invention provides a QoS-enabled digital content servicesystem and method of providing a high quality digital content service,by utilizing donor nodes.

According to an aspect of the present invention, there is provided aQoS-enabled service system on a P2P network including: a serviceprovider capable of providing digital content; one or more user nodesreceiving digital content from the service provider; one or more donornodes lending resources for providing digital content; and a supernodereceiving information on user nodes and donor nodes, and a copy ofdigital content from the service provider, allowing the exchange ofdigital content among the user nodes by P2P networking, and when atleast one user node experiences a P2P networking error during theexchange of the digital content arrange for a predetermined number ofdonor nodes from among the one or more donor nodes to join the P2Pnetworking.

The one or more user nodes may be peers belonging to a P2P networkinggroup in a predetermined area, and may be capable of communication andfile sharing with their respective communication protocols andcommunication applications.

Before obtaining digital content, the one or more user nodes mayregister in the service provider and provide their attributes to theservice provider.

The one or more donor nodes may be peers having their respectivecommunication and file sharing functions in a P2P network, may registerin the service provider, and provide their attributes to the serviceprovider.

The attributes may include information on a download and/or uploadbandwidth, the physical location of a node, a convenient time foruploading, or information on whether or not a node exists behind anetwork address translation (NAT) device or a firewall.

The sup emode may receive the attributes of the registered user nodesand donor nodes and a copy of digital content from the service provider.

Based on the attributes, the supernode may distribute the copy of thedigital content to the user nodes in the P2P network group so thatcontent information can be exchanged among the user nodes through P2Pnetworking.

If a user node having some or all of the distributed digital contentloses a P2P networking function, the supernode may contact all donornodes, ask whether or not the donor node can provide resources, select adonor node having an appropriate bandwidth, and provide the content ofthe user node that lost the P2P networking function, to the selecteddonor node, thereby connecting the donor node to the P2P network.

While finding the donor node as the replacement of the user node whichhas lost the P2P networking function and arranging for the donor node tojoin the P2P networking, the supernode itself may perform the role asthe replacement of the user node.

The supernode may be capable of selectively providing a method ofproviding QoS-enabled digital content and a method of providingQoS-non-enabled digital content to the user of the user node.

If the user node selects the method of providing QoS-enabled digitalcontent, the supernode may utilize the donor node as the replacement ofa user node which has lost the function, and if the user node selectsthe method of providing QoS-non-enabled digital content, the supernodemay not utilize the donor node even when a user node loses the function.

When donor nodes provide resources as the replacement of a function-lostuser node, the supernode may give predetermined credits to the donornodes.

The credits may be given discriminatively according to stability,performance of the resources, and number of times the doner node providethe resources.

According to another aspect of the present invention, there is provideda method of providing a QoS-enabled digital content service on a P2Pnetwork, the method including: a user node which wants to obtainpredetermined digital content, or a donor node intending to provideresources registering in a service provider providing digital content;the service node providing information on user nodes and donor nodes,and digital content to a supernode; the supernode distributing digitalcontent to user nodes, and enabling the user nodes to share the digitalcontent through P2P networking; and if an error occurs in the P2Pnetworking state of any of the user nodes, the supernode detecting theerror, and allowing a donor node provide digital content through P2Pnetworking as a replacement of the user node.

In the registering in a service provider, the user node and donor nodemay provide attributes, including information on a download and/orupload bandwidth, the physical location of the node, a convenient timefor uploading, or information on whether or not a node exists behind anNAT device or a firewall, to the service provider.

In the distributing performed by the supernode of the digital content touser nodes, and the enabling of the user nodes to share the digitalcontent through P2P networking, based on the attributes, the supernodemay distribute the copy of the digital content to the user nodes in theP2P network group so that content information can be exchanged among theuser nodes by P2P networking.

The detecting of the occurrence of the error by the supernode and theallowing of the donor node to provide digital content through P2Pnetworking as a replacement of the user node may include: if a user nodehaving some or all of the distributed digital content loses a P2Pnetworking function, the supernode contacting all donor nodes and askingwhether or not the donor node can provide resources; according to theresponses from all the donor nodes, the supernode selecting a donor nodehaving an appropriate bandwidth, and providing the content of thefunction-lost user node that lost the P2P networking function, to theselected donor node; and the supernode making the donor node join theP2P network and provide the digital content.

While finding the donor node as the replacement of the user node whichhas lost the P2P networking function and arranging for the donor node tojoin the P2P networking, the supernode itself may performs the role asthe replacement of the user node.

The method may further include, before sharing digital content amonguser nodes by P2P networking, the supernode making the user of the usernode select one of a method of providing QoS-enabled digital content anda method of providing QoS-non-enabled digital content.

If the user node selects the method of providing QoS-enabled digitalcontent, the supernode may utilize the donor node as the replacement ofa user node which has lost the function, and if the user node selectsthe method of providing QoS-non-enabled digital content, the supernodemay not utilize the donor node even when a user node loses the function.

When donor nodes provide resources as the replacement of a function-lostuser node, the supernode may give predetermined credits to the donornodes.

The credits may be given discriminatively according to stability,performance of the resources, and number of times the donor node providethe resources.

According to another aspect of the present invention, there is provideda method of downloading QoS-enabled digital content by P2P networking,including: before joining a P2P network, a user of a user node (peer)requesting a service provider having desired media content to providethe media content; the service provider receiving the request of thecontent informing a closest supernode of the request and providinginformation on the user node to the supernode; by considering peersjoining in the P2P network and the size of the media content, thesupernode informing the user node of an estimated time required forQoS-enabled download, and an estimated time required for QoS-non-enableddownload; if the user selects the QoS-enabled download and while the P2Pcontent downloading is performed, a network error occurs in one or morepeers connected to the network, the supernode finding a donor nodehaving appropriate and available replacement resources, and contactingthe donor node; while the donor node and the current user node establisha connection, the supernode performing as the peer of the network,joining in the P2P networking as a replacement of the peer in which theerror has occurred, and continuing the download of the content which thepeer has, until the donor node begins to perform the function of thepeer.

When donor nodes provide resources as the replacement of a function-lostuser node, the supernode may give predetermined credits to the donornodes.

The credits may be given discriminatively according to stability,performance of the resources, and number of times the donor nodesprovide the resources.

According to another aspect of the present invention, there is provideda method of providing a QoS-enabled video streaming service by P2Pnetworking, the method including: before streaming video data, a serviceprovider which is to provide the video data, transmitting notices,including details of the video data to be broadcast, to all users; userswho are interested in the video data from among the users receiving thenotices, making reservations (registering) with the service provider,indicating that they will participate in the broadcasting in order towatch real-time video streaming, in which the participation of thebroadcasting includes participation as a user node in order to watch thevideo data, and participation as a donor node in order to lendresources; transmitting information obtained from the users and a copyof the video content to be provided, to local supernodes; the supernodesproviding the video content to user nodes in a distributed manner, andmaking the video content broadcast to the user nodes which have reservedthe video content, through P2P network at a reserved time; and ifQoS-enabled video streaming is requested, the supernodes monitoring thevideo content broadcast state and enabling seamless video streamingservice, by utilizing a donor node as a replacement of a user node inwhich an error occurs.

When donor nodes provide resources as the replacement of a function-lostuser node, the supernode may give predetermined credits to the donornodes.

The credits may be given discriminatively according to stability,performance of the resources, and number of times the donor nodosprovide the resources

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will become moreapparent by describing in detail exemplary embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a schematic diagram illustrating an example of P2P networksystem providing QoS-enabled digital content in which digital content isdownloaded or media streaming is performed according to an exemplaryembodiment of the present invention;

FIG. 2 is a flowchart illustrating a method of providing a QoS-enabledservice according to an exemplary embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method of downloading media contentin a P2P network according to an exemplary embodiment of the presentinvention;

FIG. 4 is a flowchart illustrating a method of receiving a videostreaming service in a P2P network according to an exemplary embodimentof the present invention;

FIG. 5A is a diagram illustrating a state of a content providing systemusing P2P networking, in which digital content is normally shared byuser nodes A through E, to which digital content is distributed,according to an exemplary embodiment of the present invention;

FIG. 5B is a diagram illustrating a state of a P2P networking systemwhen a networking error occurs in a user node according to an exemplaryembodiment of the present invention; and

FIG. 5C is a diagram illustrating a state of a P2P networking system inwhich a donor node is selected by a supernode and acts as thereplacement of a user node, providing digital content according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown.

FIG. 1 is a schematic diagram illustrating an example of a P2P networksystem providing QoS-enabled digital content in which digital content isdownloaded or media streaming is performed according to an exemplaryembodiment of the present invention.

The system includes a service provider 100, user nodes A through E,donor nodes D1 through D5, and a supernode 110.

The service provider 100 has digital content and can provide a free orcharged digital content service. An example of the service provider 100may be a content server of a Disney company having a variety of movieand animation content files.

The user nodes A through E are peers belonging to a P2P networking groupin a predetermined area, and have predetermined communication protocolsand communication applications, by which a user node in the network cancommunicate with and share files with other nodes in the network. InFIG. 1, the user nodes A through E connected to and communicating witheach other are nodes that can exchange digital content provided by theservice provider 100 using P2P technology.

The user nodes A through E should access the service provider 100 andregister their attributes before obtaining digital content.

The donor nodes D1 through D5 are peers belonging or not belonging tothe P2P networking group, and like the user nodes, have communicationand file sharing functions in the network. As replacements of one ormore user nodes that have lost their functions during P2P networking,donor nodes provide their resources, thereby allowing other user nodesto utilize digital content of the user nodes which have failed.

The donor nodes D1 through D5 should also provide their attributes tothe service provider 100 and register the attributes.

When registering the attributes, the user nodes A through E or the donornodes D1 through D5 should provide their attributes to the serviceprovider 100. The attributes may be, for example, information on adownload and/or upload bandwidth, the physical location of a node, aconvenient time for uploading, or information on whether or not a nodeexists behind an NAT device or a firewall. Each user node has a uniquetoken identifier (ID) that can be used for billing or othertransactions. By using this token ID, the anonymity of peers can beguaranteed, an essential feature of a P2P network.

The supernode 110 receives attributes and digital content of theregistered user nodes A through E and registered donor nodes D1 throughD5 from the service provider 100. Based on this information, thesupernode 110 distributes digital content to the user nodes A through E,and keeps information on the digital content and related information onthe user nodes A through E.

Also, when a user node having a part or all of the distributed digitalcontent loses a P2P networking function by, for example, a randomturn-off, the supernode 110 can select a donor node which will beconnected to the P2P network and provide the digital content as areplacement of the user node. After receiving required digital contentfrom the supernode 110, the selected donor node can join the P2Pnetworking, thereby downloading and uploading digital content togetherwith other user nodes A through E.

The supernode 110 can selectively provide a method of providingQoS-enabled digital content and a method of providing QoS-non-enableddigital content so that a user node which wants to obtain the digitalcontent can select one of the methods. If the method of providingQoS-non-enabled digital content is selected, then, in the process inwhich the user node obtaining the digital content by using P2Pnetworking, even when the networking function of another user nodehaving part of its digital content lost, the supernode 110 does not needto replace the other user node with a donor node. Meanwhile, if themethod of providing QoS-enabled digital content is selected, then, whenthe networking functions of some user nodes which are P2P networked arelost, the supernode 110 substitutes donor nodes for the contentproviding functions of the user nodes.

When the donor nodes D1 through D5 provide resources instead of the usernodes which have lost their functions, the supernode 110 givespredetermined points or credits to the donor nodes D1 through D5. Thecredits may be given discriminatively according to the stability,performance, and number of times the donor nodes provide the resources.Thus given credits may be used later as necessary expenses when thedonor nodes are changed to user nodes and an attempt is made to obtainpredetermined digital content, or may be used as a means allowingQoS-enabled digital content to be provided.

When a donor violates a resource providing contract (for example,through system turn-off), or when the promised resources and performanceare not provided, the credits may be cut down.

FIG. 2 is a flowchart illustrating a method of providing a QoS-enabledservice according to an exemplary embodiment of the present invention.

First, user nodes A through E of users who want to obtain predetermineddigital content register as user nodes in the service provider 100having the digital content, or donor nodes D1 through D5 intending toprovide resources register as donor nodes in the service provider 100.When a node registers as a user node or a donor node, the node shouldprovide its attributes to the service provider 100.

In operation 210, the service provider 100 provides the attributes ofthe user nodes A through E and the donor nodes D1 through D5, and thedigital content to be provided, to the supernode 110 which is locatedclosest to the user nodes A through E. If the sup emode 100 already hasthe digital content, providing of the digital content in this operationcan be omitted.

By applying predetermined methods known to those of ordinary skill inthe art pertaining to the present invention, the supernode 110distributes the digital content to the user nodes A through E, andstores information on the user nodes, including attributes, andinformation on the donor nodes.

By performing P2P communication among the user nodes A through E havingdistributed digital content, download and/or upload of the digitalcontent are performed in operation 220.

Some of the user nodes A through E may be disconnected from the P2Pnetworking due to random turn-off or the like, and therefore thesupernode 110 checks for any disconnections in operation 230. If such adisconnection occurs, in order to guarantee QoS, the supernode 110contacts donor nodes in a donor node list, finds a donor node(s) capableof providing appropriate resources, distributes the digital contentdistributed to the disconnected user nodes, to the donor nodes, andmakes the donor node(s) participate in the P2P networking in operation240. In particular, the resources may be the bandwidth of the donornode(s), and in this case, available time information of the resourcesmay also be provided to the supernode 110.

Operation 240 may or may not be performed according to whether an optionof selecting a QoS service method, which is provided by the supernode110 to a user node that wants to use digital content, is selected by theuser of the user node. That is, if the user node selects the QoS-enabledservice method, then, in order to guarantee, seamless transmission ofthe digital content, the supernode 110 performs operation 240. If theuser node does not select the QoS-enabled service method, the supernode110 does not perform operation 240, and waits until the disconnecteduser nodes return to the network, or a new user node having the digitalcontent is connected to the network.

FIG. 3 is a flowchart illustrating a method of downloading media contentin a P2P network according to an exemplary embodiment of the presentinvention.

Before joining a P2P network, a user of a peer (user node) capable ofP2P networking registers with a service provider having a desired mediacontent file, informs the service provider that the user will requestthe digital content as a user node or will provide resources as a donornode, and provides information on the user to the service provider inoperation 300.

The service provider informs the closest supernode of this, and providesinformation on the user node and donor nodes, including attributes, tothe supernode in operation 310. The supernode may have already receivedthe digital content requested by the user from the service provider andkept the digital content, or may newly receive the digital content.

The supernode makes user nodes exchange digital content by P2Pnetworking in operation 320. The supernode may calculate an estimatedtime required for downloading the media content file according to theattributes of user nodes (peers) joining the current P2P network, andmay inform the user (node) of the calculation result together withQoS-enabled option information. In this case, information on details ofcredits of the user, and additionally required credits for downloadingthe digital content may be further provided.

For example, when the user wants to download a 5-gigabyte content fileaccording to a QoS-enabled method, a required time may be 60 minutes andthe required credits may be 2 points. This is enabled because thesupernode can distribute the digital content, by appropriately usingdonor nodes for fast downloading of the digital content.

In this example, if the user does not select the QoS-enabled method andwants to download the 5-gigabyte content file according to an ordinarymethod, the credits may not be needed at all, but the time required fordownloading the digital content may be 8 hours or more. This may bebecause of the small number of user nodes which are connected to the P2Pnetwork and they provide the digital content in a distributed manner, orbecause of unstable resource usage states of the connected user nodes.

If the user selects the QoS-enabled option in operation 340, thesupernode provides the user with seamless media content downloading forwhich a predetermined required time is guaranteed, by utilizing donornodes in operation 350. That is, if any one or more peers connected tothe network experience unexpected network errors or are turned off inoperation 330, the supernode finds a donor node which has appropriateand available replacement resources, from a list of donor nodes, andmakes the donor node provide the digital content instead of the peersdisconnected from the network in operation 350.

If the user does not select the QoS-enabled option in operation 340, thesupernode allows downloading to be performed only from among user nodesin operation 320.

While the donor node and the current user node establish a connection,the supernode may operate as a peer of the network, thereby continuingto download the digital content contained in the turned-off peer.

If the donor node replaces the turned-off peer, the supernode finishesthe P2P network connection.

FIG. 4 is a flowchart illustrating a method of receiving a videostreaming service in a P2P network according to an exemplary embodimentof the present invention.

Before streaming video data, a service provider which is to provide thevideo data sends notices including details of the video data to bebroadcast, to all users in operation 400. The details may include a timeand date for streaming the video data and other metadata.

Among the users receiving the notices, those who are interested in thevideo data may make reservations with the service provider, indicatingthat they will join the broadcasting in order to receive real-time videostreaming in operation 410. In this case, the user node of each user mayprovide the attributes, as described above, and informs whether the userwants to watch the video or to perform the role of a donor node.

Information obtained from the users and copies of the video content tobe serviced are transmitted to local supernodes in operation 420.

The supernodes may further inform the users of details of credits andhow many more credits are further required in order to download thevideo content.

The supernodes provide the video content to user nodes in a distributedmanner, and allow the video content to be broadcast to the user nodeswhich have reserved the video content service, through a P2P network ata reserved time in operation 430.

When QoS-enabled video streaming is requested, the supernodes monitorthe video content broadcast state in operation 440, and enables aseamless video streaming service, by utilizing a donor node as areplacement of a user node in which an error occurs in operation 450.These operations may be replaced by operations 360 through 390illustrated in FIG. 3.

FIGS. 5A through 5C illustrate a P2P network system in which QoS-enableddigital content according to the present invention is transmitted. FIG.5A illustrates a state in which digital content is normally shared byuser nodes A through E, to which digital content is distributed. FIG. 5Billustrates a state in which, when a networking error occurs in a usernode E, a supernode 110 continuously provides digital content instead ofthe user node E, to user nodes A through D, and F, and at the same time,contacts donor nodes D1 through D5. FIG. 5C illustrates a state in whichthe donor node D3 is selected by the supernode 110 and, the donor nodeD3 acts as the replacement of the user node E, providing digitalcontent.

According to the present invention, even when the function of a peerdoes not normally work on a P2P network, a donor as a replacement of thepeer is utilized, thereby providing QoS-enabled digital content to auser requesting the digital content.

While the present invention has been particularly shown and describedwith reference to an exemplary embodiment thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A quality-of-service (QoS)-enabled service system on a peer-to-peer(P2P) network, the system comprising: a service provider which providesdigital content; a plurality of user nodes which receive the digitalcontent from the service provider; one or more donor nodes which lendresources for providing the digital content; and a supernode whichreceives information on the user nodes and the donor nodes, and a copyof digital content from the service provider, allows exchange of digitalcontent among the user nodes by P2P networking, and if at least one usernode experiences a P2P networking error during the exchange of thedigital content, arranges for at least one donor node from among the oneor more donor nodes to join the P2P networking.
 2. The system of claim1, wherein the user nodes are peers belonging to a P2P networking groupin a predetermined area, and are capable of communication and filesharing.
 3. The system of claim 1, wherein before obtaining digitalcontent, the user nodes register with the service provider and providetheir attributes to the service provider.
 4. The system of claim 3,wherein the one or more donor nodes are peers having their respectivecommunication and file sharing functions in a P2P network, register withthe service provider, and provide their attributes to the serviceprovider.
 5. The system of claim 3, wherein the attributes includeinformation on at least one of a download and upload bandwidth, thephysical location of a node, a convenient time for uploading, orinformation on whether a node exists behind a network addresstranslation device or a firewall.
 6. The system of claim 4, wherein thesupernode receives the attributes of the registered user nodes and theregistered donor nodes and a copy of digital content from the serviceprovider.
 7. The system of claim 6, wherein based on the attributes, thesupernode distributes the copy of the digital content to the user nodesin the P2P network group so that content information can be exchangedamong the user nodes through P2P networking.
 8. The system of claim 7,wherein if a user node having some or all of the distributed digitalcontent loses a P2P networking function, the supernode contacts alldonor nodes, inquires whether the donor nodes can provide resources,selects a donor node having an appropriate bandwidth, and provides thecontent of the user node that lost the P2P networking function, to theselected donor node, thereby connecting the donor node to the P2Pnetwork.
 9. The system of claim 1, wherein while finding the at leastone donor node to join the P2P networking as a replacement of the usernode which has lost the P2P networking function and arranging for the atleast one donor node to join the P2P networking, the sup emode itselfperforms the role as the replacement of the user node.
 10. The system ofclaim 1, wherein the supernode is capable of selectively providing amethod of providing QoS-enabled digital content and a method ofproviding QoS-non-enabled digital content to the user of the user node.11. The system of claim 10, wherein if the at least one user nodeselects the method of providing QoS-enabled digital content, thesupernode utilizes the one or more donor nodes to join the P2Pnetworking as a replacement of a user node which has lost the function,and if the user node selects the method of providing QoS-non-enableddigital content, the supernode does not utilize the at least one donornode even when the user node loses the function.
 12. The system of claim10, wherein when donor nodes provide resources as the replacement, thesupernode gives predetermined credits to the donor nodes.
 13. The systemof claim 12, wherein the credits are given discriminatively according tostability, performance of the resources, and number of times the donornodes provide the resources.
 14. A method of providing a Quality ofService (QoS)-enabled digital content service on a P2P network, themethod comprising: a plurality of user nodes, and one or more donornodes registering with a service provider providing digital content; theservice provider providing information on the user nodes and the donornodes, and digital content to a supernode; the supernode distributingdigital content to user nodes, and enabling the user nodes to share thedigital content through peer-to-peer (P2P) networking; and if an erroroccurs in the P2P networking state of one of the user nodes, thesupernode detecting the error, and arranging for a donor node to providedigital content through P2P networking as a replacement of the usernode.
 15. The method of claim 14, wherein in the registering with aservice provider, the user nodes and the one or more donor nodes provideattributes, including information on a download or upload bandwidth, aphysical location of the nodes, a convenient time for uploading, or onwhether a node exists behind a network address translation device or afirewall, to the service provider.
 16. The method of claim 14, whereinin the distributing performed by: the supernode of the digital contentto user nodes, and the enabling of the user nodes to share the digitalcontent through P2P networking based on the attributes, the supernodedistributes the copy of the digital content to the user nodes in the P2Pnetwork group so that content information can be exchanged among theuser nodes by P2P networking.
 17. The method of claim 16, wherein thedetecting of the occurrence of the error by the supernode and thearranging of the donor node to provide digital content through P2Pnetworking as the replacement of the user node comprises: if a user nodehaving some or all of the distributed digital content loses a P2Pnetworking function, the supernode contacting all donor nodes andinquiring whether the donor nodes can provide resources; according toresponses from the donor nodes, the supernode selecting a donor nodehaving an appropriate bandwidth, and providing the content of the usernode that lost the P2P networking function, to the selected donor node;and the supernode making the selected donor node join the P2P networkand provide the digital content.
 18. The method of claim 17, whereinwhile finding the donor node as the replacement of the user node whichhas lost the P2P networking function and arranging for the donor node tojoin the P2P networking, the supernode itself performs the role as thereplacement of the user node.
 19. The method of claim 14, furthercomprising, before sharing digital content among the user nodes by P2Pnetworking, the supernode requesting the user node to select one of amethod of providing QoS-enabled digital content and a method ofproviding QoS-non-enabled digital content.
 20. The method of claim 19,wherein if the user node selects the method of providing QoS-enableddigital content, the supernode utilizes the donor node as thereplacement of the user node which has lost the function, and if theuser node selects the method of providing QoS-non-enabled digitalcontent, the supernode does not utilize the donor node even when a usernode loses the function.
 21. The method of claim 14, wherein when donornode provides resources as the replacement of a user node, the supernodegives predetermined credit to the donor node.
 22. The method of claim21, wherein the credit is given discriminatively according to stability,performance of the resources, and number of times the donor nodeprovides resources.
 23. A method of downloading Quality of Service(QoS)-enabled digital content by peer-to-peer (P2P) networking,comprising: a user node requesting a service provider having desiredmedia content to provide the media content before joining a P2P network;the service provider which receives the request, informing a closestsupernode of the request and providing information on the user node tothe supernode; the supernode informing the user node of an estimatedtime required for QoS-enabled download, and an estimated time requiredfor QoS-non-enabled download based on user nodes joining in the P2Pnetwork and a size of the media content; if the user node selects theQoS-enabled download and while content downloading is performed, anetwork error occurs in at least one user node connected to the network,the supernode determining a donor node having appropriate and availablereplacement resources, and contacting the donor node; and while thedonor node and the user node establish a connection, the supernodeperforming as the at least one, joining in the P2P networking as areplacement of the at least one user node in which the error hasoccurred, and continuing the download of the content which the at leastone user node has until the donor node begins to perform the function ofthe at least one user node.
 24. The method of claim 23, wherein when thedonors nodes provide resources as the replacement of the at least oneuser node, the supernode gives predetermined credit to the donor node.25. The method of claim 24, wherein the credit is given discriminativelyaccording to stability, performance of the resources, and number oftimes the donor node provides the resources.
 26. A method of providing aQuality of Service (QoS)-enabled video streaming service by peer-to-peer(P2P) networking, the method comprising: before streaming video data, aservice provider which is to provide the video data, transmittingnotices, including details of the video data to be broadcast to allusers; users who are interested in the video data from among the usersreceiving the notices, making reservations for registering with theservice provider, indicating that they will participate in thebroadcasting in order to watch real-time video streaming, in which theparticipation of the broadcasting includes participation as a user nodein order to watch the video data, and participation as a donor node inorder to lend resources; transmitting information obtained from theusers and a copy of the video content to be provided, to localsupernodes; the supernodes providing the video content to a plurality ofuser nodes in a distributed manner, and making the video contentbroadcast to the user nodes which have reserved the video content,through P2P network at a reserved time; and if QoS-enabled videostreaming is requested, the supernodes monitoring the video contentbroadcast state and enabling seamless video streaming service, byutilizing a donor node as a replacement of a user node in which an erroroccurs.
 27. The method of claim 26, wherein when the donor nodes provideresources as the replacement of the user node, the supernode givespredetermined credits to the donor nodes.
 28. The method of claim 27,wherein the credits are given discriminatively according to stability,performance of the resources, and number of times the donor nodesprovide the resources.